MRI is an apparatus for applying RF magnetic field to an examinee disposed under magnetostatic field to detect an echo signal occurring in the examinee and subjecting the detected echo signal to signal processing, thereby imaging the echo signal. A Time-of-flight method (hereinafter referred to as TOF method) is general as a blood-vessel imaging method in the MRI apparatus. Particularly, with respect to sites such as four limbs, there have been recently used a method of imaging blood vessels by using a sequence of repetitively irradiating these sites with RF pulses at a short time interval to image these sites under the state that magnetization is set to a stationary state (SSFP).
This SSFP pulse sequence does not take on blood vessel depicting performance which is dependent on blood stream velocity as in the case of the TOF method, but depicts, as high signals, blood, spinal fluid, synovial fluid, bladder, fat, etc. which have long T2 values because obtained signals are represented by T2/T1(√T2/T1)). Therefore, this method is one of imaging methods which take over from the TOF method with respect to four limbs, etc. which are relatively low in blood stream velocity.
A pre-saturation method is used as a method of selectively depicting each of artery and vein (patent document 1, patent document 2, etc.). According to this method, an imaging area is set vertically to blood vessel running of an examinee to perform blood stream imaging. At this time, spins of an area adjacent to the imaging area are pre-excited before the imaging area is excited, thereby suppressing a signal from a blood stream flowing into the imaging area. Accordingly, the blood stream flowing in the opposite direction to the blood stream flowing from the pre-excited area to the imaging area is selectively depicted. The pre-exciting pulse is called as pre-saturation pulse, and the pre-excited area is hereunder referred to as pre-saturation area.    Patent Document 1: JP-A-10-248825    Patent Document 1: JP-A-7-327956